STN1 is a component of the CST complex, a complex that binds to single-stranded DNA and is required for protecting telomeres from DNA degradation. The CST complex binds single-stranded DNA with high affinity in a sequence-independent manner, while isolated subunits bind DNA with low affinity on their own. In addition to telomere protection, the CST complex probably has a more general role in DNA metabolism at non-telomeric sites. This entry represents the C-terminal region of Stn1 which has two winged helix-turn-helix (wHTH) motifs, wHTH1 and wHTH2 [2,4]. wHTH1 is structurally similar to that in RPA32 with a large insertion between helices alpha2 and alpha3, unique to Stn1, that may allow interaction with a different set of proteins that function at telomeres such as Ctc1 [4]. wHTH2 is most similar to the DNA-binding wHTH motifs of the pur operon repressor and RepE replication initiator, but it does not bind double-stranded DNA [5].

1: A DNA polymerase-{alpha}{middle dot}primase cofactor with homology to replication protein A-32 regulates DNA replication in mammalian cells. Casteel DE, Zhuang S, Zeng Y, Perrino FW, Boss GR, Goulian M, Pilz RB; J Biol Chem. 2009;284:5807-5818. PMID:19119139

2: OB fold-containing protein 1 (OBFC1), a human homolog of yeast Stn1, associates with TPP1 and is implicated in telomere length regulation. Wan M, Qin J, Songyang Z, Liu D; J Biol Chem. 2009;284:26725-26731. PMID:19648609

3: RPA-like mammalian Ctc1-Stn1-Ten1 complex binds to single-stranded DNA and protects telomeres independently of the Pot1 pathway. Miyake Y, Nakamura M, Nabetani A, Shimamura S, Tamura M, Yonehara S, Saito M, Ishikawa F; Mol Cell. 2009;36:193-206. PMID:19854130

4: Structure of the human telomeric Stn1-Ten1 capping complex. Bryan C, Rice C, Harkisheimer M, Schultz DC, Skordalakes E; PLoS One. 2013;8:e66756. PMID:23826127

5: Stn1-Ten1 is an Rpa2-Rpa3-like complex at telomeres. Sun J, Yu EY, Yang Y, Confer LA, Sun SH, Wan K, Lue NF, Lei M; Genes Dev. 2009;23:2900-2914. PMID:20008938